I have LEDs on my nav and position lights, reversed polarity so 2 conductors manage both lights. Many of the LEDs were burned over the years so it was coming time to fix that, the whole assembly was quite expensive as most things on boat shops but I got a bag of LEDs for 1/50th of the cost and rewired the thing.
It had 3 led in series with a limiting resistor for each 3 lights, is what makes the most sense anyway. I tried a few experiments running individual LEDs with it's own resistors so when one goes bad only that one get's off but didn't worked, it was too much heat inside and the things burned because of the heat. I wanted to add zener diodes in parallel with each LED so when it burns, the others in the serie remains on, but two problems there, one is the working area to solder them on the air as the whole assembly originally was and the second one would be when the other polarity is selected the current would be forward in those zeners, that could be fixed with two diodes, one for each light. IIRC white LEDs where 2 in series, red and green 3.
The whole assembly was a piece of PVC pipe with two lines of holes all arround, one for each LED, PVC caps, the bottom one had an electrical tube for screwing and taking wires out, the top cap two LEDs for the wind indicator, when the nav light is on. Luckyly for me I don't hit too many things with my mast, but the wind indicators (one mechanical and one electronic) and the VHF antenna would hit first and are more expensive so I can't advice much on resilience. You could pot the whole thing but it's tricky to get some potting compound that conducts heat, doesn't contract while setting, takes nice the thermal cycles and don't break connections, etc. I guess using a sturdy metal pipe and use a similar construction to mine should do, I would have to see if I have the photos somewhere but it seems like a pretty common type of light since LED are around.
JS